Surface display of glycosylated Tyrosinase related protein-2 (TRP-2) tumour antigen on Lactococcus lactis

Recombinant L. lactis vaccine LL-plSAM-WAE targeting four virulence factors provides mucosal immunity against H. pylori infection

BACKGROUND

Helicobacter pylori (H. pylori) causes chronic gastric disease. An efficient oral vaccine would be mucosa-targeted and offer defense against colonization of invasive infection in the digestive system. Proteolytic enzymes and acidic environment in the gastrointestinal tract (GT) can, however, reduce the effectiveness of oral vaccinations. For the creation of an edible vaccine, L. lactis has been proposed as a means of delivering vaccine antigens.

RESULTS

We developed a plSAM (pNZ8148-SAM) that expresses a multiepitope vaccine antigen SAM-WAE containing Urease, HpaA, HSP60, and NAP extracellularly (named LL-plSAM-WAE) to increase the efficacy of oral vaccinations. We then investigated the immunogenicity of LL-plSAM-WAE in Balb/c mice. Mice that received LL-plSAM-WAE or SAM-WAE with adjuvant showed increased levels of antibodies against H. pylori, including IgG and sIgA, and resulted in significant reductions in H. pylori colonization. Furthermore, we show that SAM-WAE and LL-plSAM-WAE improved the capacity to target the vaccine to M cells.

CONCLUSIONS

These findings suggest that recombinant L. lactis could be a promising oral mucosa vaccination for preventing H. pylori infection.

Recent advances in genetic tools for engineering probiotic lactic acid bacteria

Synthetic biology has grown exponentially in the last few years, with a variety of biological applications. One of the emerging applications of synthetic biology is to exploit the link between microorganisms, biologics, and human health. To exploit this link, it is critical to select effective synthetic biology tools for use in appropriate microorganisms that would address unmet needs in human health through the development of new game-changing applications and by complementing existing technological capabilities. Lactic acid bacteria (LAB) are considered appropriate chassis organisms that can be genetically engineered for therapeutic and industrial applications. Here, we have reviewed comprehensively various synthetic biology techniques for engineering probiotic LAB strains, such as clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 mediated genome editing, homologous recombination, and recombineering. In addition, we also discussed heterologous protein expression systems used in engineering probiotic LAB. By combining computational biology with genetic engineering, there is a lot of potential to develop next-generation synthetic LAB with capabilities to address bottlenecks in industrial scale-up and complex biologics production. Recently, we started working on Lactochassis project where we aim to develop next generation synthetic LAB for biomedical application.

Deciphering the substrate specificity of housekeeping sortase A and pilus-specific sortase C of probiotic bacterium Lactococcus lactis

Several strains and species of lactic acid bacteria (LAB) are widely used in fermented foods, including dairy products and also as probiotics, because of their contribution to various health benefits in humans. Sortase enzymes decorate the bacterial cell wall with different surface proteins and pili for facilitating the interactions with host and environment for the colonization and beneficial effects. While the sortases and sortase anchored proteins from pathogens have been the prime focus of the research in the past, sortases from many non-pathogenic bacteria, including LAB strains, have attracted attention for their potential applications in vaccine delivery and other clinical interventions. Here, we report the purification and functional characterization of two sortases (housekeeping SrtA and pilus-specific SrtC) from a probiotic Lactococcus lactis. The purified sortases were found to be active against the putative LPXTG motif-based peptide substrates, albeit with differences. The in-silico analysis provides insights into the residues involved in substrate binding and specificity. Overall, this study sheds new light on the aspects of structure, substrate specificity, and function of sortases from non-pathogenic bacteria, which may have physiological ramifications as well as their applications in sortase-mediated protein bioconjugation.

Biotechnological Innovations and Therapeutic Application of Pediococcus and Lactic Acid Bacteria: The Next-Generation Microorganism

Lactic acid bacteria represent a worthwhile organism within the microbial consortium for the food sector, health, and biotechnological applications. They tend to offer high stability to environmental conditions, with an indicated increase in product yield, alongside their moderate antimicrobial activity. Lack of endotoxins and inclusion bodies, extracellular secretion, and surface display with other unique properties, are all winning attributes of these Gram-positive lactic acid bacteria, of which, Pediococcus is progressively becoming an attractive and promising host, as the next-generation probiotic comparable with other well-known model systems. Here, we presented the biotechnological developments in Pediococcal bacteriocin expression system, contemporary variegated models of Pediococcus and lactic acid bacteria strains as microbial cell factory, most recent applications as possible live delivery vector for use as therapeutics, as well as upsurging challenges and future perspective. With the radical introduction of artificial intelligence and neural network in Synthetic Biology, the microbial usage of lactic acid bacteria as an alternative eco-friendly strain, with safe use properties compared with the already known conventional strains is expected to see an increase in various food and biotechnological applications in years to come as it offers better hope of safety, accuracy, and higher efficiency.

In vitro disease modeling of oculocutaneous albinism type 1 and 2 using human induced pluripotent stem cell-derived retinal pigment epithelium

Oculocutaneous albinism (OCA) encompasses a set of autosomal recessive genetic conditions that affect pigmentation in the eye, skin, and hair. OCA patients display reduced best-corrected visual acuity, reduced to absent ocular pigmentation, abnormalities in fovea development, and/or abnormal decussation of optic nerve fibers. It has been hypothesized that improving eye pigmentation could prevent or rescue some of the vision defects. The goal of the present study was to develop an in vitro model for studying pigmentation defects in human retinal pigment epithelium (RPE). We developed a “disease in a dish” model for OCA1A and OCA2 types using induced pluripotent stem cells to generate RPE. The RPE is a monolayer of cells that are pigmented, polarized, and polygonal in shape, located between the neural retina and choroid, with an important role in vision. Here we show that RPE tissue derived in vitro from OCA patients recapitulates the pigmentation defects seen in albinism, while retaining the apical-basal polarity and normal polygonal morphology of the constituent RPE cells.

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We established a human iPSC-based in vitro model for oculocutaneous albinism (OCA)

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iRPE derived from OCA-iPSC retains apical-basal polarity and polygonal morphology

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OCA-iRPE recapitulates the pigmentation defect seen in albinism

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Excess pre-melanosomes and scarce mature melanosomes are found in OCA-iRPE

Genetic tools for the development of recombinant lactic acid bacteria

Lactic acid bacteria (LAB) are a phylogenetically diverse group with the ability to convert soluble carbohydrates into lactic acid. Many LAB have a long history of safe use in fermented foods and are recognized as food-grade microorganisms. LAB are also natural inhabitants of the human intestinal tract and have beneficial effects on health. Considering these properties, LAB have potential applications as biotherapeutic vehicles to delivery cytokines, antigens and other medicinal molecules. In this review, we summarize the development of, and advances in, genome manipulation techniques for engineering LAB and the expected future development of such genetic tools. These methods are crucial for us to maximize the value of LAB. We also discuss applications of the genome-editing tools in enhancing probiotic characteristics and therapeutic functionalities of LAB.

Molecular dynamics simulation and experimental study of the surface-display of SPA protein via Lpp-OmpA system for screening of IgG

Staphylococcal protein A (SpA) is a major virulence factor of Staphylococcus aureus. S. aureus is able to escape detection by the immune system by the surface display of protein A. The SpA protein is broadly used to purify immunoglobulin G (IgG) antibodies. This study investigates the fusion ability of Lpp'-OmpA (46-159) to anchor and display five replicate domains of protein A with 295 residues length (SpA295) of S. aureus on the surface of Escherichia coli to develop a novel bioadsorbent. First, the binding between Lpp'-OmpA-SPA295 and IgGFc and the three-dimensional structure was investigated using molecular dynamics simulation. Then high IgG recovery from human serum by the surface-displayed system of Lpp'-OmpA-SPA295 performed experimentally. In silico analysis was demonstrated the binding potential of SPA295 to IgG after expression on LPP-OmpA surface. Surface-engineered E. coli displaying SpA protein and IgG-binding assay with SDS-PAGE analysis exhibited high potential of the expressed complex on the E. coli surface for IgG capture from human serum which is applicable to conventional immune precipitation.

Identification and characterization of a moonlighting protein-enolase for surface display in Streptococcus thermophilus

Background

Streptococcus thermophilus is an important food starter and receiving more attention to serve as cell factories for production of high-valued metabolites. However, the low yields of intracellular or extracellular expression of biotechnological and biomedical proteins limit its practical applications.

Results

Here, an enolase EnoM was identified from S. thermophilus CGMCC7.179 with about 94% identities to the surface-located enolases from other Streptococcus spp. strains. The EnoM was used as an anchor to achieve surface display in S. thermophilus using GFP as a reporter. After respectively mixing the GFP-EnoM fusion protein or GFP with S. thermophilus cells in vitro, the relative fluorescence units (RFU) of the S. thermophilus cells with GFP-EnoM was 80-folds higher than that with purified GFP. The sharp decrease in the RFU of sodium dodecyl sulfate (SDS) pretreated cells compared to those of non-pretreated cells demonstrated that the membrane proteins were the binding ligand of EnoM. Furthermore, an engineered β-galactosidase (β-Gal) was also successfully displayed on the cell surface of S. thermophilus CGMCC7.179 and the relative activity of the immobilized β-Gal remained up to 64% after reused 8 times. Finally, we also demonstrated that EnoM could be used as an anchor for surface display in L. casei, L. bulgaricus, L. lactis and Leuconostoc lactis.

Conclusion

To our knowledge, EnoM from S. thermophilus was firstly identified as an anchor and successfully achieved surface display in LAB. The EnoM-based surface display system provided a novel strategy for the enzyme immobilization.

Targeting Melanoma Hypoxia with the Food-Grade Lactic Acid Bacterium Lactococcus Lactis

Melanoma is the most aggressive form of skin cancer. Hypoxia is a feature of the tumor microenvironment that reduces efficacy of immuno- and chemotherapies, resulting in poor clinical outcomes. Lactococcus lactis is a facultative anaerobic gram-positive lactic acid bacterium (LAB) that is Generally Recognized as Safe (GRAS). Recently, the use of LAB as a delivery vehicle has emerged as an alternative strategy to deliver therapeutic molecules; therefore, we investigated whether L. lactis can target and localize within melanoma hypoxic niches. To simulate hypoxic conditions in vitro, melanoma cells A2058, A375 and MeWo were cultured in a chamber with a gas mixture of 5% CO₂, 94% N₂ and 1% O₂. Among the cell lines tested, MeWo cells displayed greater survival rates when compared to A2058 and A375 cells. Co-cultures of L. lactis expressing GFP or mCherry and MeWo cells revealed that L. lactis efficiently express the transgenes under hypoxic conditions. Moreover, multispectral optoacoustic tomography (MSOT), and near infrared (NIR) imaging of tumor-bearing BALB/c mice revealed that the intravenous injection of either L. lactis expressing β-galactosidase (β-gal) or infrared fluorescent protein (IRFP713) results in the establishment of the recombinant bacteria within tumor hypoxic niches. Overall, our data suggest that L. lactis represents an alternative strategy to target and deliver therapeutic molecules into the tumor hypoxic microenvironment.

FimH-based display of functional eukaryotic proteins on bacteria surfaces

The demand for recombinant proteins for analytic and therapeutic purposes is increasing; however, most currently used bacterial production systems accumulate the recombinant proteins in the intracellular space, which requires denaturating procedures for harvesting and functional testing. We here present a novel FimH-based expression system that enables display of fully functional eukaryotic proteins while preventing technical difficulties in translocating, folding, stabilizing and isolating the displayed proteins. As examples, Gaussia Luciferase (GLuc), epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and epiregulin (EPRG) were expressed as FimH fusion proteins on the surface of E. coli bacteria. The fusion proteins were functionally active and could be released from the bacterial surface by specific proteolytic cleavage into the culture supernatant allowing harvesting of the produced proteins. EGFR ligands, produced as FimH fusion proteins and released by proteolytic cleavage, bound to the EGF receptor (EGFR) on cancer cells inducing EGFR phosphorylation. In another application of the technology, GLuc-FimH expressed on the surface of bacteria was used to track tumor-infiltrating bacteria by bioluminescence imaging upon application to mice, thereby visualizing the colonization of transplanted tumors. The examples indicate that the FimH-fusion protein technology can be used in various applications that require functionally active proteins to be displayed on bacterial surfaces or released into the culture supernatant.

Engineering E. coli cell surface in order to develop a one-step purification method for recombinant proteins

Sortases are enzymes mostly found in Gram-positive bacteria which cleave proteins site-specifically. This feature makes them a promising tool in molecular biology and biotechnology. In this study, using bacterial surface display of recombinant proteins and ability of sortase A in site-specifically cleavage of the amino acid sequences, a novel method for one-step purification of recombinant proteins was developed. Using computational program tools, a chimeric protein containing a metallothionein (mt) and chitin binding domain (ChBD) was attached to the C-terminal domain of the truncated outer membrane protein A (Lpp'-ompA) using sortase recognition site (amino acid residues: LPQTG) as a separator. The structure of the chimeric protein was simulated using molecular dynamics to determine if the LPQTG motif is accessible to the sortase active site. The designed chimeric protein was expressed and purified. The purified chimeric protein was also displayed on the surface of E. coli cells. Both purified chimeric protein and the E. coli cells displaying Lpp'-ompA-mt-ChBD carrier protein were then treated with sortase to evaluate the efficiency of sortase-mediated cleavage of purified chimeric protein as well as surface displayed-chimeric protein. It is shown that mt-ChBD protein was successfully cleaved and dissociated from Lpp'-ompA carrier and released into the medium after treatment with sortase in both recombinant protein and surface displayed-chimeric protein. The experimental results confirmed the molecular dynamics analysis results. The presented method could be regarded as a novel strategy for one step expression and purification of recombinant proteins.

Autodisplay of an avidin with biotin-binding activity on the surface of Escherichia coli

OBJECTIVES

To display a recombinant avidin fused to the autotransporter ShdA to bind biotinylated molecules on the surface of Escherichia coli.

RESULTS

Two chimeric protein constructs containing avidin fused to the autotransporter ShdA were expressed on the surface of Escherichia coli DH5α. One fusion protein contained 476 amino acids of the ShdA α and β domains, whereas the second consisted of a 314 amino acid from α and truncated β domains. Protein production was verified by SDS-PAGE using an antibody to the molecular FLAG-tag. The surface display of the avidin-shdA fusion protein was confirmed by confocal microscopy and flow cytometry analysis, and the biotin-binding activity was evaluated by fluorescence microscopy and flow cytometry using biotin-4-fluorescein and biotinylated-ovalbumin (OVA).

CONCLUSIONS

Expression of a recombinant avidin with biotin-binding activity on the surface of E. coli was achieved using the autotransporter ShdA. This system is an alternative to bind biotinylated molecules to E. coli.

Lactococcus lactis As a Versatile Vehicle for Tolerogenic Immunotherapy

Genetically modified Lactococcus lactis bacteria have been engineered as a tool to deliver bioactive proteins to mucosal tissues as a means to exert both local and systemic effects. They have an excellent safety profile, the result of years of human consumption in the food industry, as well as a lack of toxicity and immunogenicity. Also, containment strategies have been developed to promote further application as clinical protein-based therapeutics. Here, we review technological advancements made to enhanced the potential of L. lactis as live biofactories and discuss some examples of tolerogenic immunotherapies mediated by mucosal drug delivery via L. lactis. Additionally, we highlight their use to induce mucosal tolerance by targeted autoantigen delivery to the intestine as an approach to reverse autoimmune type 1 diabetes.

A review on Lactococcus lactis: from food to factory

Lactococcus lactis has progressed a long way since its discovery and initial use in dairy product fermentation, to its present biotechnological applications in genetic engineering for the production of various recombinant proteins and metabolites that transcends the heterologous species barrier. Key desirable features of this gram-positive lactic acid non-colonizing gut bacteria include its generally recognized as safe (GRAS) status, probiotic properties, the absence of inclusion bodies and endotoxins, surface display and extracellular secretion technology, and a diverse selection of cloning and inducible expression vectors. This have made L. lactis a desirable and promising host on par with other well established model bacterial or yeast systems such as Escherichia coli, Saccharomyces [corrected] cerevisiae and Bacillus subtilis. In this article, we review recent technological advancements, challenges, future prospects and current diversified examples on the use of L. lactis as a microbial cell factory. Additionally, we will also highlight latest medical-based applications involving whole-cell L. lactis as a live delivery vector for the administration of therapeutics against both communicable and non-communicable diseases.